Information

South Carolina's Bald Eagles - Mortality

Shooting has historically been the most significant cause of mortality in eagles. Between 1961 and 1965, 62 percent of eagles found dead were shot. More recently, the percentage of eagles that died as a result of illegal shooting has declined to under 20 percent. This is undoubtedly one major reason for eagle recovery. Delisting the bald eagle may mislead the public by inferring that eagles are no longer protected and could result in increased shooting mortality. Additionally, when eagles lose protection under the Endangered Species Act, they may lose much of the habitat protection currently afforded to the species. This may lead to habitat degradation that can make current and future nesting habitat unsuitable.

Chemical contamination of eagle habitat has long been a problem for this top carnivore. Eagles have been shown to be sensitive to a variety of toxins, particularly persistent organo-chlorine pesticides, such as DDT. A ban on widespread use of DDT was implemented in 1972. Since then, an array of effective pesticides has been developed that have limited impacts on non-target species. Overall, pesticide poisoning has been greatly reduced and is another reason for recovery of the species. However, even with many new products on the market, the problem persists.

Lead poisoning in eagles has also been identified as a significant problem. However, non-toxic shot has been required for waterfowl hunting. A more recent source of poisoning is from barbiturates at landfills where eagles feed on animals that have been euthanized. Deposition
of mercury in eagle foraging habitat also poses a potential threat to the health of bald eagle populations.

Currently there are two emerging diseases affecting eagles. West
Nile virus (WNV) and Avian
Vacuolar Myelinopathy (AVM) have both been identified as new sources of eagle mortality. Recovery of the bald eagle population will result in larger concentrations of eagles and less fit individuals as a result of competition. This may lead to an increased risk of disease.

Finally, other significant sources of mortality in eagles include electrocution at power lines and collision trauma. A variety of raptor safe power line configurations have been developed and are available from the Avian Power Line Interaction Committee.